Increased concerns over diseases transmitted via bodily fluids, such as Acquired Immune Deficiency Syndrome (AIDS) or Hepatitis B, have dramatically increased the search for methods and means of preventing their spread. In the last decade this has led to the development of dozens of devices designed to decrease the incidence of accidental contact with contaminated medical sharps, such as the needles of used syringes. While these devices demonstrate at least minimal utility, many of them have designs which are unnecessarily complicated, require alterations to the instruments with which they are used, or are limited in their degree of protection.
Among the guards or shields disclosed for use with medical syringes are those found in U.S. Pat. Nos. 4,631,057 (Mitchell), 4,737,144 (Chokai), 4,871,355 (Kikkawa), and 4,946,447 (Hardcastle et al.).
The Mitchell patent discloses a tubular needle guard which can be telescoped over a collar mounted on a syringe to a position in which the guard protectively covers the syringe's needle. The Mitchell device's requirement of a separate collar adds critical internal and external dimensional requirements as well as unnecessary production steps and costs.
U.S. Pat. No. 4,737,144, issued to Chokai, teaches a similar tubular syringe needle guard which telescopes over the surface of a syringe until retention means, associated with the guard and the syringe's barrel, lock the guard in an extended position covering the syringe's needle. While the Chokai device does not require the collar associated with the Mitchell invention, it is only useful with specifically engineered syringes. Such syringes must have an annular slot towards the rear of the syringe barrel to receive the guard's retention means while the guard is in its retracted position, as well as an accompanying ramp intersecting the annular slot to guide the retention means from the slot. Furthermore, the locking mechanism disclosed by Chokai requires a specific, sharply angled type of annular recess to retain the guard in its extended position. Since the Chokai locking mechanism is designed to slide on the ramp associated with the rear annular slot, it would not secure the guard to syringes having more gradually sloped forward surfaces.
U.S. Pat. No. 4,871,355, issued to Kikkawa, provides a telescoping needle protection chamber for use with blood collection tubes. This chamber is designed to telescope along a needle-beating blood collection tube between a first position in which the needle is exposed and a second in which the needle is within the protection chamber, with the chamber being releasably locked in each position. The Kikkawa releasable locking system allows an operator to manually move the protection chamber relative to the collection tube by applying a manual sliding force in the desired direction. While this allows easy and flexible operation, the lack of a more secure means of maintaining the protection chamber in the second position creates a potential for unintended exposure of used needles and accidental needle sticks.
U.S. Pat. No. 4,946,447, issued to Hardcastle et al., discloses a syringe-protecting sleeve which comprises a body split such that it has a longitudinal slit or aperture extending its entire length. This split body is snapped onto a syringe and may be slid over the syringe in a telescoping manner to cover the syringe's needle. This split guard also comprises a tab means which, when the guard is extended over the needle, contacts an axial wall at the distal end of the syringe to prevent the guard from sliding back along the syringe body to expose the needle. Such a design may be unsatisfactory for two reasons, the first being that the slightly greater than semicircular design may allow the guard to be removed unexpectedly or allow small fingers to pass through the longitudinal opening to contact the needle. In addition, the locking mechanism disclosed, like that of the Chokai invention, is designed to work with an axial wall and would not be effective with syringes having more gradually sloped forward surfaces.
In view of the limitations of the prior art, there continues to be a need for relatively uncomplicated needle guards that are useful in protecting against accidental punctures. There is a further need for such safety devices which do not require modification of already existing instruments, such as conventional syringes or preprepared syringe cartridges.